Inserting tool for tangless coils



Feb. 26, 1952 J. o. FORSTER INSERTING TOOL FOR TANGLESS COILS 2SHEETS-SHEET 1 Filed March 2, 1949 FIG. 2.

. INVENTOR. JOHN FORS TER BY W h m Feb. 26, 1952 J. o. FORSTER INSERTINGTOOL FOR TANGLESS COILS 2 SHEETS-SHEET 2 Filed March 2, 1949 FIG. Z

FIG. 4.

INVENTOR. FORSTER M ATTORNEY Patented e1). 26, 1952 2,586,805 INSERTINGTOOL FOR TANGLESS COILS John 0. Forster, Long Island City, N. Y.,assignor,

by mesne assignments, to Heli-Coil Corporation, Long Island City, N. Y.,a corporation of Delaware Application March 2, 1949, Serial No. 79,260 9Claims. (01. 1o' 1) The resent invention relates to a tool for insertingthread-forming wire coils in tapped holes. In making screw connections,the tapped holes of boss or nut members are frequently lined withinserts of coiled wire in order to provide, for engagement with bolts orstuds, an interior threading having qualities which the material of theboss or nut member is lacking. For instance, if a hard steel bolt orstud is to be secured in an aluminum boss, the wire insert of proper material will protect the soft aluminum against damages resulting from arepeated screwing in and out of the bolt. Usually, such inserts havespringy properties and are coiled with an original diameter larger thanthat of the boss thread they are intended to reinforce. For that reason,special tools are necessary for inserting such wire coils. Theconventional tools for that purpose require that at least one endconvolution of each insert is specifically shaped in order to rendersuch tools applicable. This is a severe drawback as in the production ofinserts, the specific formation of the end convolutions calls foroperations which are additional to the coiling of the Wire and increaselabor and production costs considerably. Certain types of theconventional inserting tools even require additional operations afterthe insertion of a coil in order to remove an end needed for renderingthe tool applicable but obstructing the passage of a member intended tobe screwed into the insert; in many cases of The invention also aims toprovide an attachment for use with a power-driven shaft and a tool ofthe class of screw drivers to which the afore-mentioned tool broadlybelongs, for the purpose of preventing the screw member from injuringthe threading into which it is to be driven.

Further objects and details of the invention will be apparent from thedescription given hereinafter and the accompanying drawing illustratingan embodiment thereof by way of example. In the drawing,

Fig. l is a longitudinal cross-section of a tool according to theinvention;

Figs. 2, 3 and 4 are cross-sections along lines 2-2; 3-3 and 4-4,respectively, of Fig. 1;

Fig. 5 is a cross-section similar to Fig. 2, with the gripping elementsin projected position;

Fig. 6 illustrates a coil of the type to which the tool may be applied,and

Fig. 7 is an elevation, on a smaller scale, of the tool in engagementwith such coil.

Referring now to the drawing, a cylindrical shank I0 is provided with anupper extension piece ll including an end portion 12 of reduced diameterfor the purpose of applying a torque to the shank. The shank and theextension are use of such tanged coils, the tang has to be re:-

moved after the insertion.

The present invention aims to provide a tool which can be introducedinto a cylindrical tangless coil from the one coil end, and can becaused to grip the other coil end so as to hold it firmly and, ifnecessary, to apply a torque thereto as it is required in the case of ascrew thread insert.

The tool according to the invention essentially comprises a cylindricalmember of a diameter somewhat smaller than the inner diameter of thecoil for which it is destined, and at least one element connected tothat member so as to be oscillatable with respect thereto to projectfrom or be withdrawn within the periphery of said member whereby the endof a coil can be gripped between said element and said member.

In the preferred form of the tool, resilient means are provided tendingto urge said element in the projected position, and other means towithdraw it against the restraint of said resilient means.

Another object of the invention aims to provide a tool of the mentionedtype with means adapting it for power operation.

axially alined by means as indicated at [3. The shank has an axial holeM in its upper portion with a diametrically extending slot l5. On theone side of the hole [4 a pin l6 crossing the slot I5 is secured in theshank. On pin [6, a lever I1 is pivoted one arm l8 of which projectsoutsubstantially forms a hollow cylinder with a bottom 21 having anaxial bore 28 in which the mentioned pin 2| is axially guided with itslower end 29 of somewhat increased diameter. Intermediate its upper endand its bottom, piece 25 is provided with an inner flange 30. An endpiece 3| is attached to the bottom 21, seated on it at 32 and having anaxial bore 33, through which the end 29 of pin 21 projects. The lowersurface of the bottom 21 is recessed so as to form at least one gap 34of a shape apparent from Fig. 2 between the bottom 21 and the end piece3|, in which gap a gripping element 35 is lodged, Al,-

though one is sufiicient, there are two such gaps 34 and elements 35shown in the illustrated embodiment for a reason to be explainedhereinafter, but there may be even more than two if so desired. Eachgripping element, as best seen in Fig. 2, is approximately pear-shaped,i. c. it has a rounded portion from which there extends a portion havingconverging sides. The element has in its lower surface a recess 36 whichextends, curved and tapering, from the one 31 of the converging sides tothe rounded portion 38 so that there is only a thin wall 39 standing onthe other one of the converging sides. That wall is curved substantiallyaccording to the periphery of the mentioned cylindrical parts 25 and ofthe tool. Each element 35 is secured to a pivot pin 40 which isjournaled in the bottom 21 and flange 30 of the piece 25 so that theelement can swing outward in the position of Fig. and inward in theposition of Fig. 2. Thus, it will be clear, that each element35 can bedefined as a hook projectable from and retractable within thecircumference of the tool body. Each pin 40 projects upward into thespace between the flange 30 of piece 25 and the lower face 4| of theshank l0 where a tension spring 42 is attached with its one end to asecondary pin 43 radially projecting from pin 40, and with its other endto another pin 44 projecting upwards from the flange 30 as best seen inFig. 4. The arrangement is such that the spring tends to turn the pin 40so as to urge the element 35 in its outward position of Fig. 5,. In thespace between the fiange 30 and the upper face 45 of the bottom 21 ofpiece 25, a radial finger 46 extending in a direction .opposite to thatof the associated element35 is secured to each pin 40 so as tocooperate, substantially in the manner of a cam device, with a conicalpiece 41, which is mounted on rod 2| and bears against the shoulder 48formed by the lower end 29 of that rod. A compression spring 49surrounding the rod for its major portion intericrly of the tubularmember 24, is inserted between the conical piece 41 and shank ID. Thisspring. urges the piece 41 together with rod 2 I. downward, whereby thefinger or fingers 46 are urged outwardly to turn the element or elements35 inward against the restraint of the small springs 42. The shank l0,piece 25 and the end piece 3| are held together and in proper relativeposition by bolts 50 appearing in cross-section in Figs. 2 to 4.

The tool as far as described hereinbefore, is applicable in thefollowing manner: While all parts are in the position of Fig. 1, thatmeans whilev the gripping elements35 are retracted, an insert coil ofthe type illustrated in Fig. 6 is pushed from below on the tool untilits lower end convolution is above the gripping elements 35. The coilwire may be of any desired cross-section which in the illustratedexample is selected as substantially diamond shaped. While the coil isso held in relation to the tool, lever arm |8 will be depressed therebylifting rod 2| together with the cone 41 against the restraint of spring49. The lifting of the cone frees the fingers 46 so that the springs 42in Fig. 4 can turn the pins 40 to swing the fingers inward and thegripping elements 35 outwards into the position of Fig. 5. By loweringthe insert coil and turning it relatively to the tool, the lower coilend 52 can be .passed through the channel 36, from its wider end, of oneof the gripping elements 35. It is advisable to provide the tool withmore than one gripping element in order to shorten the maximum angle thecoil will have to be turned in order so to engage such element. It willalso be by hand or by power.

understood, that, for oppositely coiled inserts, gripping elements ofmirror image shape are to be used in order to permit the coil end toenter the wider end of the channel 36. Similarly, in that event, thearrangement of the fingers 46 must be a mirror image of that shown andthe springs 42 must be arranged so as to turn the pins 40 in theopposite direction. When the end 52 of the coil convolution engaging thechannel 36 slightly projects from the narrow end of the latter, leverarm |8 will be released, whereupon spring 49 urges the cone 41 downwardwhich will spread the fingers 46 so that the gripping elements areturned inward. Thereby, as shown in Figs. 2 and 1., the gripping elementwith the coil convolution will clamp the latter between three points,viz. the pointed end 53 of the element, the pin 40 which projects intothe channel 36, and a point or short face portion 54 rounded off thebottom part. 21. The insert coil 5| so held may then be inserted in atapped hole such as 14 in Fig. 7, to be lined by screwing it in with theaid of the tool. When the end 29 towards the end of the screwingoperation engages a stop which may either be the bottom 16 of a blindhole or a stop otherwise provided if it is a through-going hole, the rod2| will be pushed upward in relation to thefurther advancing toolthereby releasing the grip of the element 35 on the coil end which dueto the continued turning of the tool will slip out of the channel 36,whereupon the tool can be removed.

The tool just. described may be either operated Now, I have found thatfrequently the threading of a, tapped hole is damaged, if an externallythreaded element, be it a stud or bolt or an insert coil the outerportions of which constitute an outer threading, is to be driven intothe hole by means of a shaft which is moved simultaneously in an axialand peripheral direction as e. g. by the shaft of a tapping or screwdriving machine. Unless extreme care is taken to insurethat the leadingconvolution end of the screw member and the end of the thread groove ofthe tapped member are exactly in registry when the one member starts toengage the other one, the one of harder material will cut into thesofter and destroy its thread.

In order to avoid such happening I provide, according to my invention,an attachment to the tool end to which the axial and peripheral movementof the power driveis to be transmitted. This attachment comprises meansfor positive rotation of the tool and other means for the axial drivethereof, including a lost motion connection operative against therestraint of a spring, wherein the lost motion connection is effectiveover a distance of approximately the pitch of the combined axial andperipheral advancement of the driving shaft to which the attachment isto be connected, and wherein the spring force is less than would benecessary to cause a cutting effect of the above-mentioned kind.

For this purpose, the afore-mentioned upper extension |2 of the shank I0is provided with an axial bore 69, and with a longitudinal groove 6| onits outside. A socket 63 has an axial bore 64 to receive therein,fittingly, the extension l2. A disc 65 bears on the bottom of bore 64.The disc is recessed at 66 and accommodates in that recess the one endof a compression spring 61 the other end of which bears on the bottom ofthe bore 60 housing the major length of the spring. A screw 68 isscrewed into a radially-tapped hole 69 of the socket and projectsinwardly with its end 19 which constitutes a key in engagement with thegroove 6'! thereby forming a lost motion connection between theextension I2 and socket 63 and also connecting these members for commonrotation. The upper end H of the socket 63 is so shaped that it can berigidly but releasably secured to the shaft of a suitable machine as e.g. a drill press ,or tapping machine. For this purpose, the upper end His shown as a slender cone in the illustrated embodiment.

In order to apply a power drive to the tool with the attachment justdescribed, the conical end II will be inserted into the end of anaccordingly shaped driving shaft 12 indicated in dash and dot lines.-While the parts are in the position of Fig. 1, a wire coil may bepushed on the shank from below until the lower convolution has clearedthe gripping elements 35. Thereupon the lever I! may be operated ashereinbefore described. However, it is preferable to provide astationary abutment 13 which will depress the lever arm I 8 when theshaft 12 with the tool is lifted, and release arm It When the shaft islowered. If the tool rotates during the engagement of the lever arm andthe abutment, the latter may be shaped as a ring co-axial with the tool.In all other respects, the gripping and clamping of the coil end takesplace as stated above. The shaft with the tool and the gripped coil maybe lowered while turning in order to insert the latter in an interiorlythreaded bore such as 14 of boss member 15 in Fig. 7. When, then, thelower portion of the tool enters the hole 14 and the lowermost coilconvolution engages the top surface of the boss 15, the coil end, inmost instances, will not be exactly in registry with the groove entranceof the tapped hole. While, now, the shaft 12 continues to rotate anddescend, shank ID with the coil thereon will also be rotated. However,owing to the lost motion connection BI, the shank will not be presseddown with a force stronger than required to overcome the restraint ofthe'spring Bl. In consequence, the coil can be turned without axialmovement until its end can enter the threading of the hole 14. In allother respects, the inserting operation is similar to that explainedabove.

Although I have described my invention in connection with wire coilinserts for tapped holes, it will be clear that it can be applied, withequal advantage, to any kind of wire coil, for instance, a cylindricalspring in order to contract or expand it by turning the one end thereofin relation to the other.

Furthermore, although I have described and shown only one embodiment ofmy invention it will be apparent to those skilled in the art that manyalterations and modifications thereof are possible without departurefrom the spirit and essence of my invention which for that reason shallnot be limited but by the scope of the appended claims.

I claim:

1. A tool for inserting cylindrical wire coils in tapped holescomprising a cylindrical body including means to apply a torque thereto,said body being provided with a first recess in its periphery, an'element reciprocably mounted to said body within said first recess soas to be projectable from and retractable within the periphery of saidbody, said element including an outer rim bordering a second recess ofsaid element so that when said element is projected there is an entranceinto said second recess between said outer rim and the periphery of saidbody for an end convolution of a coil into which the tool has beeninserted, and means interiorly of said body and in engagement with saidelement to reciprocate the latter, thereby to clamp said convolutionhaving entered said second recess between said rim and said body whensaid element is at least partly retracted.

, 2. A tool for inserting cylindrical wire coils in tapped holes,comprising a cylindrical body including means to apply a torque thereto,said body being provided with a recess in its periphery, an elementreciprocably mounted to said body within said recess and including aportion having a substantially hook-like cross-section and beingprojectable from and retractable within the periphery of said body, saidelement being adapted to engage with said hook-like crosssection an endconvolution of a wire coil into which said tool has been inserted and toclamp it against said body, and means interiorly of said body and inengagement with said element to reciprocate the latter.

3. A tool as claimed in claim 2, said element being a fiat piecesubstantially pear-shaped and pivoted in' said recess with its pointedportion projectable from and retractable within said body periphery,said piece being recessed on one of its fiat surfaces so as to form achannel extending taperingly from one of the sides close to the pointedend of the element to the other side close to the rounded portionthereof.

4. A tool as claimed in claim 2 further comprising a pivot pin in saidrecess parallel to the body axis, said element being turnable about theaxis of said pivot pin for the projection and retraction of itshook-like portion.

5. A tool as claimed in claim' 2 further comprising a spring connectedto said element and said body and tending to urge said element intoprojected position, resilient means operatively connected to saidelement so as to urge said element into retracted position against therestraint of said spring, and operative means in connection with saidresilient means to shift the latter into an inoperative position.

6. A tool as claimed in claim 2 further com prising a pivot in said bodyacross said recess, said element being reciprocable about the axis ofsaid pivot, a first spring connected to said element and said body andtending to turn said element into projected position, a cam deviceconnected to said element interiorly of said body and including adriving part, a driven part and a second spring, said driven part beingconnected to said element, said second spring being connected to saiddriving part so as to urge it in one direction thereby to cause saiddriven part to turn said element into retracted position against therestraint of said first spring, and operative means in connection withsaid driving part to shift the latter in the opposite direction againstthe restraint of said second spring.

7. A tool as claimed in claim 5 wherein said driven part of the camdevice is an arm connected to said element and projecting radially inrespect to said pivot axis, and said driving part is a coneshaped piecemovable axially in respect to the axis of said body.

8. A tool for inserting cylindrical wire coils in tapped holescomprising a cylindrical body including means at one of its ends toapply a torque thereto and being provided with a recess in itsperiphery, an element reciprocably mounted to said body within saidrecess and including a portion having a substantially hook-likecrosssection and being projectable from and retractable within theperiphery of said body, said element being adapted to engage with saidhooklike cross-section an end convolution of a wire coil .into which.said tool has been inserted and to clamp it against .said body, .a firstspring connected to said element and said body tending to project saidhook-like portion, means in operative connection with said elementinteriorly of said body and including a second spring tending to retractsaid hook-like portion, and a rod-like member axially shiftable withrespect to said body and projecting from the other end thereof, saidmember being connected to said means so as to inactivate the latter bycompression of said second spring when the projecting portion of saidmember is shifted inwards.

9. A tool as claimed in claim 8 further comprising a lever pivoted insaid body and having one arm in engagement with said rod-likememher andits other arm projecting laterally from said body, so as to shift saidmember when said other arm is operated.

JOHN O. FORSTER.

REFERENCES CITED The following references are of record in the 1 file ofthis patent:

UNITED STATES PATENTS Number Name Date 533,585 Ekehorn -n Feb. 5, 18951,312,737 Krueger Aug. 12, 1919 2,371,622 Hawkins Mar. 20, 1945

